Ransack for a weapon (5)
I believe the answer is:
rifle
I believe this is a double definition.
'ransack' is the first definition.
(rifle can mean to ransack or rob)
'for a weapon' is the second definition.
(rifle is a kind of weapon)
(Other definitions for rifle that I've seen before include "Ransack; a weapon" , "loot in sack" , "Security provider with stock" , "Ransack - firearm" , "Standard military gun fired from shoulder" .)